Title page for ETD etd-03132009-040440

Negative photoaxis of mosquito larvae as a potential tool in the rapid bilogical monitoring of aquatic wastes (Diptera: Culicidae)

Degree

Master of Science

Department

Entomology

Advisory Committee

Advisor Name

Title

Turner, E. Craig Jr.

Committee Chair

Cochran, Donald G.

Committee Member

Grayson, James McD.

Committee Member

Kok, Loke T.

Committee Member

Simmons, George M. Jr.

Committee Member

Keywords

Culicinae

Date of Defense

1975-02-05

Availability

unrestricted

Abstract

A little-known approach to toxicity testing--based on negative
phototaxis of larval Aedes aegypti--was investigated as a contribution
to the search for rapid methods applicable to the field of water pollution
control. Zinc and copper were the toxicants tested. All tests
were conducted with a standard "synthetic" dilution water.

A mosquito colony was established to provide a uniform supply
of test larvae. Preliminary tests were performed on the acute toxicity
of zinc and copper against A. aegypti larvae, as well as tests
on larval growth and development at various concentrations of the
metals.

For the photomigration toxicity tests, two juxtaposed troughs
were used, one containing the test solution, the other a control.
Third instar larvae migrated away from a six-watt fluorescent light
for two minutes per run. This was repeated at intervals until 50%
were unable to migrate 50 cm in 120 sec. Photographs were taken of
the larval migrations. From the pictures an empirical criterion was
derived (the 40-cm, 60-sec ET50) through a series of graphical interpolations. All inactivation analyses were based on this criterion.

From time-inactivation regression lines, exponential toxicity
curves were obtained by interpolation. The curves were of an unusual
shape, depicting the characteristic nature of the dosage-response.

The sensitivity of the inactivation technique was comparable to
that of the acute toxicity tests. However, inactivation was far
quicker; depending on concentration, it occurred within one to five
hours. By all methods used in this study, zinc and copper were judged
to be slow-acting and of low overall toxicity. Copper was, however,
consistently more toxic than zinc by at least one order of magnitude.
The ET50 in 10 ppm Cu++ was 147 min.; in 10 ppm Zn++, it was 209 min.

Some possible improvements in technique were discussed. It was
suggested that the photornigration approach to toxicity testing can be
of definite practical use to biologists in water pollution control.